Electrical device having magnetically doped topological insulator quantum well film

Abstract

An electrical device includes an insulating substrate and a magnetically doped TI quantum well film. The insulating substrate includes a first surface and a second surface. The magnetically doped topological insulator quantum well film is located on the first surface of the insulating substrate. A material of the magnetically doped topological insulator quantum well film is represented by a chemical formula of Cr y (Bi x Sb 1-x ) 2-y Te 3 , wherein 0<x<1, 0<y<2, and values of x and y satisfies that an amount of a hole type charge carriers introduced by a doping with Cr is substantially equal to an amount of an electron type charge carriers introduced by a doping with Bi, the magnetically doped topological insulator quantum well film is in 3 QL thickness to 5 QL thickness.

What is claimed is: 
     
       1. An electrical device, comprising:
 an insulating substrate comprising a first surface and a second surface; and 
 a magnetically doped topological insulator quantum well film located on the first surface of the insulating substrate; 
 wherein a material of the magnetically doped topological insulator quantum well film is represented by a chemical formula of Cr y (Bi x Sb 1-x ) 2-y Te 3 , wherein 0<x<1, 0<y<2, and values of x and y satisfies that the amount of a hole type charge carriers introduced by a doping with Cr is substantially equal to the amount of an electron type charge carriers introduced by a doping with Bi; and the magnetically doped topological insulator quantum well film is in a range of 3 QL thickness to 5 QL thickness, and the material of the magnetically doped topological insulator quantum well film is represented by a chemical formula of Cr 0.15 (Bi 0.10 Sb 0.9 ) 1.85 Te 3 . 
 
     
     
       2. The electrical device of  claim 1 , wherein the insulating substrate has a dielectric constant larger than 5000 at a temperature equal to or smaller than 10 Kelvin. 
     
     
       3. The electrical device of  claim 2  further comprising a gate electrode, and the gate electrode is located on the second surface of the insulating substrate. 
     
     
       4. The electrical device of  claim 1  further comprising two conducting electrodes spaced from each other and located on a surface of the magnetically doped topological insulator quantum well film, the two conducting electrodes are arranged at two opposite sides of the magnetically doped topological insulator quantum well film, and a first direction is from one of the two conducting electrodes to another of the two conducting electrodes. 
     
     
       5. The electrical device of  claim 4  further comprising three output electrodes E 1 , E 2 , and E 3  spaced from each other and located on a surface of the magnetically doped topological insulator quantum well film, a direction from E 1  to E 2  is the first direction, a second direction is from E 2  to E 3 , and the first direction is substantially perpendicular to the second direction. 
     
     
       6. The electrical device of  claim 5 , wherein the magnetically doped topological insulator quantum well film has a shape comprising a rectangle central part, two first connecting parts extended from the rectangle central part to the two conducting electrodes, and three second connecting parts extended from the rectangle central part to the E 1 , E 2 , and E 3 . 
     
     
       7. The electrical device of  claim 6 , wherein the three second connecting parts extend along the second direction. 
     
     
       8. The electrical device of  claim 5  further comprising a fourth output electrode E 4  spaced from E 1 , E 2 , and E 3 , and located on the surface of the magnetically doped topological insulator quantum well film; a direction from E 3  to E 4  is the first direction; and a direction from the E 1  to E 4  is the second direction. 
     
     
       9. The electrical device of  claim 8 , wherein the magnetically doped topological insulator quantum well film comprises a rectangle central part, two first connecting parts extended from the rectangle central part to the two conducting electrodes, and four second connecting parts respectively extended from the rectangle central part to E 1 , E 2 , E 3 , and E 4 ; and a length of the rectangle central part in the second direction is smaller than a length of each of the two conducting electrodes. 
     
     
       10. The electrical device of  claim 4 , wherein the two conducting electrodes have a trapezoid shape. 
     
     
       11. The electrical device of  claim 1 , wherein a material of the insulating substrate comprises strontium titanate or Al 2 O 3 . 
     
     
       12. The electrical device of  claim 1  further comprising a liquid top gate structure located on a surface of the magnetically doped topological insulator quantum well film. 
     
     
       13. The electrical device of  claim 1 , wherein a carrier density of the magnetically doped topological insulator quantum well film is below 1×10 13  cm −2 .